A hybrid vehicle (which may hereinafter be mentioned as “vehicle”), which uses both an engine and a generator motor as a drive apparatus, carries out regenerative braking to operate the generator motor as a generator at the time of braking, and stores electric power generated in the regenerative braking in a battery. At the time of running and acceleration, the generator motor operates as an electric motor (motor) upon reception of electric power supplied from the battery, thereby assisting insufficiency of the engine output (e.g., Patent Document 1). Such a conventional drive apparatus does not discharge the regenerative braking energy at the time of braking as heat, but stores it in the battery to be used as drive energy at the time of driving and acceleration. Accordingly, the hybrid vehicle can improve the fuel consumption and reduce the total amount of the combusted exhaust gas.
The generator motor which operates as a generator may be simply called a generator, and the generator motor which operates as a motor may be simply called a motor herein. Patent Document 1: Japanese Unexamined Patent Publication No. 2005-151633
However, while the conventional drive apparatus can charge the battery at the time of braking, it cannot carry out rotational driving of the generator to acquire electric power when the motor is assisting the engine. At the time of idling, electric power for charging the battery cannot be acquired. In addition, the motor in the hybrid vehicle often assists the engine for keeping running or for acceleration or the like. Therefore, the conventional drive apparatus which converts the kinetic energy of the vehicle to electric power and stores the electric power cannot sufficiently store electric power needed to drive the motor. Because the conventional drive apparatus discharges a combusted exhaust gas which contains a substance to be used as fuel and has heat energy, it is insufficient to improve the fuel consumption of the vehicle and reduce the total amount of the combusted exhaust gas (total amount of harmful substances contained in the combusted exhaust gas).